This invention relates to thermal recording, and more specifically, to a thermal recording method using physical changes and enabling stable recording while causing only minimal changes with the passing of time, a thermal recording medium used in the method and a method for producing said recording medium.
This invention can be effectively applied to printing figures and the like corresponding to the contents of magnetic recording in a prepaid magnetic card such as a telephone card to enable the magnetically recorded contents to be macroscopically seen.
Conventionally, there are two methods for recording information on a recording paper by heating the heating element of a thermal head at desired timing according to recording signals while scanning said thermal head over the recording paper. These methods consist of a heat transcription method in which a desired pattern is transcribed on a normal recording paper by heating and melting the ink of a heat sensitive ink ribbon which is interposed between a thermal head and the recording paper, and a thermal method in which a thermal recording paper is colored in a desired pattern.
Since ink is not applied to a recording paper and the heat sensitive layer of the recording paper itself is colored in the thermal method, this method is advantageous because the printed record is not affected almost entirely even when external frictional force is applied to the recording paper after recording. This method is advantageous also because no ink ribbons are necessary.
However, since a layer containing a heat sensitive color former is used as the heat sensitive layer of a recording paper used in the conventional thermal method and said heat sensitive layer is colored due to chemical changes of said color former during heating, sufficiently good quality of the printed record is difficultly obtained because the degree of coloring may vary depending on environmental conditions, and also the stability of recording is not sufficient yet.